Or HaChaim on Exodus 33:23/אור החיים על שמות ל״ג:כ״ג

1 וראית את אחורי, "you will see My back, etc." The essence of G'd is, of course, not divisible into "front" and "back." G'd is aware of the desire of all His creatures to "see" how His light spells the continued existence of His universe. At the same time it is impossible by definition that any creature can behold this light as it would spell its doom. What did G'd do? He surrrounded His Essence with a kind of "curtain" or screen in order to diffuse the light which would otherwise have proved too blinding. The creation of such a screen created the impression in the beholder that there is something in "front" and something at the "back" of such a screen. When we look at man who is composed of spirit and body, we peceive his body as his "back," and his spirit as his "front", or "face." The "light" that G'd's Essence has made accessible to the spiritually most advanced human being is called "back," whereas the "light" He has screened out is called "front" as it is beyond the screen. This is what G'd meant when He said: "you will see "My Back" but you cannot see "My Face."

2It is also possible that the very mention by G'd of His "face" immediately after mention of His "back," i.e. אחורי ופני, indicated that even the part of Him that He described as "My Back" contained a "face;" however, G'd had arranged that only the rear of that two sided spirit or "light" would be visible so as to provide the prophet with some idea of when he faced a Divine presence.

3The word אחורי may have been employed to indicate that Moses would be very close to perceiving G'd's Essence, that He did not "hide" behind multiple screens. If there had remained several "screens" between G'd's Essence and Moses, G'd would have spoken of Achorey Achoray, and not simply of Achoray. Any intelligent and sincere servant of G'd will make only minimum eye contact with his Creator [in other words not look at Heaven beseechingly while engaged in prayer. Ed.] when bowing down during prayer.